I believe it's 8 afm lifters. 4cyl and 2 per cyl?
so this guy explains it in a way that made sense to me while researching this before buying the truck.
a lot of guys here have been in this much longer and they have seen more and know more than me. I just try to go with what makes sense at the time. I can always be wrong about everything lol.
but the idea. normal lifters get oil from the block to pump up the hydraulic part of the lifter that makes it a hydraulic lifter. these afm have a added oil hole that comes from the top. it releases pins that collapses the lifter inside so it "turns off" that cyl.
well that is the part that fails most of the time they stay down and don't pop back up. it starts tapping and eats itself alive trashing the whole motor. so short of replacing it all. the best you can do is have it not release those pins. to do that you need to block off the oil supply. that's what you did by turning it off in the tune. but those solenoids do fail and leak oil, which can release them even when electricity turned off. so to stop that there's a bushing you put under the oil pressure sensor. that's where the solenoids get they're oil from. that solves leaking solenoids.. the other way oil can get there is remember that bottom hole in the lifter that gets oil from the block. well as the internal lifter bores wear, oil can bypass from there and up thru the afm release hole. if the solenoid is closed, pressure can build up and release the pins. so if you see the towers under your vlom, that's the oil ports down to the lifter, and there's a gasket there. his trick is to cut a slot in that gasket, so any oil that bypasses internally of the lifter is harmlessly returned to the pan. that's also why you don't put a non afm vlom plate on a engine with the afm lifters still in it. you don't want that top part sealed off. once you put none afm lifters in, you do.
that's why I said while you have it apart, I'd pull the trays, take a look at the rollers to see any signs of damage, peek down at the cam lobe if you can. if all looks good, replace trays cause plastic and and old now. reuse your lifters, don't mix up what hole they came from and it would be cheap insurance short of a full delete.
he's got tear down videos of the lifters themselves and how to release stuck lifters if they do stick on you at some point.
the other side would be to replace the afm lifters, but yeah they seem overly expensive to me, and you should really do new vlom and solenoids at the same time. at that point youre at full delete money, but you did save pulling the cam and stuff. I'm not sure v4 helps your mph at all thou. on my hybrid one it actually is useful since it can stay in 4 mode a lot of the time with the help of electric motors but I decided to block it all off and clip the gaskets instead of pulling heads and doing the lifters and vlom replacement. I have hopes it will last a long time this way.
